Fibrinogen　is　a　plasma　glycoprotein　that　is　an　established　cardiovascular　risk　and　it　participates　in　the　blood-clotting　mechanism.　Nitrated　fibrinogen　has　been　shown　to　inhibit　platelet　aggregation　and　thrombus　formation.　However,　there　are　only　a　few　reports　relating　to　the　activity　and　structural　changes　of　nitrified　fibrinogen　when　metal　ions　are　present　in　the　reaction.　Mn　(II)　ion　plays　an　important　physiological　role　in　the　nervous　system　and　cardiac　function.　In　this　study,　we　use　UV-Vis,　3D-fluorescence,　SDS-PAGE　electrophoresis　and　Von-Clauss　to　detect　3-nitrotyrosine　(3-NT)　production　and　the　activity　changes　of　fibrinogen　after　nitration　and　oxidation　damage　caused　by　ONOO-　in　the　presence　of　Mn　(II).　Results　showed　that　Mn　(II)　can　enhance　the　production　of　3-NT　in　fibrinogen,　promote　fluorescence　quenching　of　fibrinogen,　and　increase　the　injury　to　gamma　and　A　alpha　chains　of　fibrinogen　in　the　presence　of　peroxynitrite.　Consequently,　Mn　(II)　promotes　concentration　dependent　fibrinogen　nitrification　damage　and　significantly　reduces　the　biological　activity　of　nitrified　fibrinogen.